相关论文: Quantifying Hidden Symmetry in the Tetragonal CH$_…
Halide perovskite (HP) semiconductors exhibit unique strong coupling between the electronic and structural dynamics. The high-temperature cubic phase of HPs is known to be entropically stabilized, with imaginary frequencies in the…
In this study, we report a tetragonal perovskite structure of SrIrO$_3$ (P4/mmm, a = 3.9362(9) \r{A}, c = 7.880(3) \r{A}) synthesized at 6 GPa and 1400 $\deg$C, employing the ambient pressure monoclinic SrIrO$_3$ with distorted 6H structure…
The hybrid halide perovskite CH3NH3PbI3 exhibits a complex structural behaviour, with successive transitions between orthorhombic, tetragonal and cubic polymorphs at ca. 165 K and 327 K. Herein we report first-principles lattice dynamics…
In the development of highly efficient photovoltaic cells, solid perovskite systems have demonstrated unprecedented promise, with the figure of merit exceeding nineteen percent of efficiency. In this paper, we investigate the optical and…
Perovskite photovoltaic ABX$_3$ systems are being studied due to their high energy-conversion efficiencies with current emphasis placed on pure inorganic systems. In this work, synchrotron single-crystal diffraction measurements combined…
CH3NH3PbI3 perovskite is nowadays amongst the most promising photovoltaic materials for energy conversion. We have studied by ab-initio calculations, using several levels of approximation - namely density functional theory including…
In this paper we analyze the band-structure of two-dimensional (2D) halide perovskites by considering structures related to the simpler case of the series, (BA)$_2$PbI$_4$, in which PbI$_4$ layers are intercalated with butylammonium…
Halide perovskites have emerged as one of the most interesting materials for optoelectronic applications due to their favorable properties, such as defect-tolerance and long charge carrier lifetimes, which are attributed to their dynamic…
Quantum confinement not only reshapes electronic states but also reorganizes the vibrational landscape of low-dimensional semiconductors. In halide perovskites, however, the role of confinement in governing symmetry effects on vibrational…
The mechanical properties of hybrid perovskite materials are important for device flexibility, resistance to fracture, epitaxial growth, surface energetics of quantum dots, and induction or relief of stress in thin films due to thermal…
Structural stability, electronic structure and optical properties of CH3NH3BaI3 hybrid perovskite is examined both from theory as well as experiment. Solution-processed thin films of CH3NH3BaI3 exhibited a high band gap of approximately…
The recently developed information-theoretic approach to crystallographic symmetry classifications and quantifications in two dimensions (2D) from digital transmission electron and scanning probe microscope images is adapted for the…
The symmetry was examined using neutron diffraction method on Pb(Zn1/3Nb2/3)O3 -9%PbTiO3 (PZN/9PT) which has a composition at the morphotropic phase boundary (MPB) between Pb(Zn1/3Nb2/3)O3 and PbTiO3. The results were compared with those of…
A large class of phononic crystals and mechanical metamaterials exhibit glide symmetry that dictates their functionality or exceptional performance. The glide symmetry gives rise to a number of intriguing phenomena like sticking-bands and…
In the last decade, hybrid organic-inorganic halide perovskites have emerged as a new type of semiconductor for photovoltaics and other optoelectronic applications. Unlike standard, tetrahedrally bonded semiconductors (e.g. Si and GaAs),…
Halide perovskites constitute a chemically-diverse class of crystals with great promise as photovoltaic absorber materials, featuring band gaps between about 1 and 3.5 eV depending on composition. Their diversity calls for a general…
Electronic and stability properties of quasi-2D alkylammonium perovskites are investigated using density functional theory (DFT) calculations and validated experimentally on selected classes of compounds. Our analysis is focused on…
The structure and ground state electronic structure of the recently synthesized SrPdO$_3$ perovskite [A. Galal {\em et al.}, J. Power Sources, {\bf 195}, 3806 (2010)] have been studied by means of screened hybrid functional and the GW…
By means of single-crystal X-ray diffraction we have revealed the breaking of centrosymmetry when lowering the temperature under T$_s$ = 200 K concomitantly with the setting of a commensurate superstructure in the small A-site quadruple…
Determining the finite temperature structure of the hybrid perovskite MAPbI3 is a challenge for both experimental and theoretical methods. A very powerful computational method that can resolve the atomic structure is molecular dynamics…